高中数学三角函数公式知识点sin =的对边 / 斜边cos =的邻边 / 斜边tan =的对边 / 的邻边cot =的邻边 / 的对边Sin2A=2SinA?CosACos2A=CosA2-SinA2=1-2SinA2=2CosA2-1tan2A=(2tanA)/(1-tanA2)(注：SinA2 是sinA的平方 sin2(A)sin3=4sinsin(/3+)sin(/3-)cos3=4coscos(/3+)cos(/3-)tan3a = tan a tan(/3+a) tan(/3-a)sin3a=sin(2a+a)=sin2acosa+cos2asinaAsin+Bcos=(A2+B2)(1/2)sin(+t)，其中sint=B/(A2+B2)(1/2)cost=A/(A2+B2)(1/2)tant=B/AAsin+Bcos=(A2+B2)(1/2)cos(-t)，tant=A/Bsin2()=(1-cos(2)/2=versin(2)/2cos2()=(1+cos(2)/2=covers(2)/2tan2()=(1-cos(2)/(1+cos(2)tan+cot=2/sin2tan-cot=-2cot21+cos2=2cos21-cos2=2sin21+sin=(sin/2+cos/2)2tan(A/2)=(1-cosA)/sinA=sinA/(1+cosA);cot(A/2)=sinA/(1-cosA)=(1+cosA)/sinA.sin2(a/2)=(1-cos(a)/2cos2(a/2)=(1+cos(a)/2tan(a/2)=(1-cos(a)/sin(a)=sin(a)/(1+cos(a)cos(+)=coscos-sinsincos(-)=coscos+sinsinsin()=sincoscossintan(+)=(tan+tan)/(1-tantan)tan(-)=(tan-tan)/(1+tantan)sin+sin = 2 sin cossin-sin = 2 cos sincos+cos = 2 cos coscos-cos = -2 sin sintanA+tanB=sin(A+B)/cosAcosB=tan(A+B)(1-tanAtanB)tanA-tanB=sin(A-B)/cosAcosB=tan(A-B)(1+tanAtanB)sinsin =/2coscos = /2sincos = /2cossin = /2sin(-) = -sincos(-) = costan (a)=-tansin(/2-) = coscos(/2-) = sinsin(/2+) = coscos(/2+) = -sinsin() = sincos() = -cossin() = -sincos() = -costanA= sinA/cosAtan(/2+)=-cottan(/2-)=cottan()=-tantan()=tan